Nurturing and being a caretaker makes the Big Heart the happiest. Giving, supporting, being there for somebody in crisis or somebody who wants to share some story or feeling about their life. Listening, offering wisdom, solutions or affection satisfies this part of the Big Heart's desire.
Reminding you that this is only one line in the hand, and that 2/3 of the population has more than one heart line type, this could carry less weight of other heart line types are dominant. Or if you also have a Hermit (this is the most common combination I see on hands when there are two heart lines types: the Big Heart and Hermit) sometimes the Hermit may be in affect and the Big Heart is put on the back burner. But it doesn't last long because giving, nurturing and caretaking are so important to feeling satisfies for the Big Heart.